Using Errors by Guard Honeybees (Apis mellifera) to Gain New Insights into Nestmate Recognition Signals.

Although the honeybee (Apis mellifera) is one of the world most studied insects, the chemical compounds used in nestmate recognition, remains an open question. By exploiting the error prone recognition system of the honeybee, coupled with genotyping, we studied the correlation between cuticular hydrocarbon (CHC) profile of returning foragers and acceptance or rejection behavior by guards. We revealed an average recognition error rate of 14% across 3 study colonies, that is, allowing a non-nestmate colony entry, or preventing a nestmate from entry, which is lower than reported in previous studies. By analyzing CHCs, we found that CHC profile of returning foragers correlates with acceptance or rejection by guarding bees. Although several CHC were identified as potential recognition cues, only a subset of 4 differed consistently for their relative amount between accepted and rejected individuals in the 3 studied colonies. These include a unique group of 2 positional alkene isomers (Z-8 and Z-10), which are almost exclusively produced by the bees Bombus and Apis spp, and may be candidate compounds for further study.

Nestmate recognition cues in the honey bee: differential importance of cuticular alkanes and alkenes.

In social insects, recognition of nestmates from aliens is based on olfactory cues, and many studies have demonstrated that such cues are contained within the lipid layer covering the insect cuticle. These lipids are usually a complex mixture of tens of compounds in which aliphatic hydrocarbons are generally the major components. The experiments described here tested whether artificial changes in the cuticular profile through supplementation of naturally occurring alkanes and alkenes in honeybees affect the behaviour of nestmate guards. Compounds were applied to live foragers in microgram quantities and the bees returned to their hive entrance where the behaviour of the guard bees was observed. In this fashion we compared the effect of single alkenes with that of single alkanes; the effect of mixtures of alkenes versus that of mixtures of alkanes and the whole alkane fraction separated from the cuticular lipids versus the alkene fraction. With only one exception (the comparison between n-C(19) and (Z)9-C(19)), in all the experiments bees treated with alkenes were attacked more intensively than bees treated with alkanes. This leads us to conclude that modification of the natural chemical profile with the two different classes of compounds has a different effect on acceptance and suggests that this may correspond to a differential importance in the recognition signature.